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Bruce
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QFA7 & 8 Dispatch Questions

Sun Oct 27, 2013 1:24 pm

This is one of the longest possible 747 flights. Looking at some of the flightaware data for them it appears they operate beyond the published range for the aircraft. According to Boeing, the range for a Boeing 747-400 is listed as 7260nm (8354sm).

QFA8 DFW-BNE is planned at 8713sm. Yesterday's run flew 8561sm, the day before flew 8357sm.
QFA7 SYD-DFW is enroute now, planned at 8585sm. In fact, the last 5 days of QFA7 have all been 8500-8800sm.

Are all of these flights flown with weight restrictions, allowing them to carry more fuel for more range? Of course there is a maximum limit of how much fuel can fit in the tanks, I wonder how much they carry? Does Qantas operate this flight with standard seating configuration or some reduced passenger setup (like all biz class)? And if they have to go out weight restricted every day how can this route be profitable? I'm intrigued at how they can operate this with a normal B744 on a daily basis.

Bruce
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longhauler
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RE: QFA7 & 8 Dispatch Questions

Sun Oct 27, 2013 2:55 pm

You have to view the process to understand how they do it.

Each day is assessed separately, starting with Flight Dispatch, usually about 2 hours before departure. They start by looking at the conditions at DFW that day, to see the MTOW. With the tremendous facilities there, it is unlikely anything less than MTOW is possible. (unless it is very very hot, and even with long runways, that is rare there is a restriction.)

Then the routing is built using a minimum time track (minimum fuel). The planned load is used, as load will affect fuel burn. The flight planning comupter will show if it flight is possible. There are two possible restrictions ... either the load is too heavy, or the volume limitations of the fuel tanks can not carry enough. (In other words, either the airrcaft can not lift the required fuel, or it can not carry the required fuel ... they are different).

If the load is heavy there are things that can be done. Re-route cargo, (through LAX for eg), cap the load at present sales, or restrict non-revs.

If that still is not enough, or if the tanks can not carry the requried fuel, then an en-route stop must be made.

Qantas, when planning the route would have used historical data condtions. And clearly, they thought the flight could be completed the majority of the time or it would not be here. I understand the DFW-BNE flight can be completed non-stop most of the time.
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Bruce
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RE: QFA7 & 8 Dispatch Questions

Sun Oct 27, 2013 3:59 pm

So then the maximum published range for an aircraft is not really a "hard" limit? I only see one diverted run of this flight on the flightaware history so it looks like it has good reliability - or maybe Qantas' disaptchers are just really really good at what they do   But all of them exceed Boeing's numbers.
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longhauler
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RE: QFA7 & 8 Dispatch Questions

Sun Oct 27, 2013 5:02 pm

Range is actually very much a grey area. The best case scenario ... which would be a runway and conditions that allow MTOW, as well as circumstances that allow being able to fill the fuel tanks ... is pretty rare.

With regard to this particular flight, I would guess that Qantas' Flight Dispatchers have it down to an art, and no kilo is left unaccounted for!

For fun (I have an odd view of fun), I ran a few flight plans through our flight planning computer, just ... "to see". One that sticks out in my mind, is running an A321 with 174 passengers (our full cabin) with baggage from YVR-HNL with an OGG alternate. This was built with full ETOPS extra fuel, and still it was possible, with a little open weight! Yet ... if you ask just about every a-netter on here, they'd say it couldn't be done!
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N243NW
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RE: QFA7 & 8 Dispatch Questions

Sun Oct 27, 2013 7:53 pm

Quoting Bruce (Thread starter):
I'm intrigued at how they can operate this with a normal B744 on a daily basis.

Keep in mind that this is not a "normal" 744, but rather one of QF's 744ERs, with GE engines and additional fuel capacity and range. QF had no choice but to run this route with a normal 744 about a month ago and had to fly DFW-AKL-BNE-SYD on the way back westbound.

As already mentioned, the nice thing is that DFW rarely imposes limits on MTOW, except on extremely hot nights or the occasional strong wind directly from the west, in which case 31L/R aren't long enough to accommodate the departure.
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Gemuser
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RE: QFA7 & 8 Dispatch Questions

Sun Oct 27, 2013 11:45 pm

Quoting N243NW (Reply 4):

Keep in mind that this is not a "normal" 744, but rather one of QF's 744ERs, with GE engines and additional fuel capacity and range

From the Boeing web site:
B774 typical range: 7260 nm
B744ER typical range: 7670 nm

So the ER typically has an extra 410 nm range over the ordinary B744, plus all those factors longhauler wrote about above.

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RE: QFA7 & 8 Dispatch Questions

Sun Oct 27, 2013 11:56 pm

Quoting Bruce (Reply 2):
I only see one diverted run of this flight on the flightaware history so it looks like it has good reliability - or maybe Qantas' disaptchers are just really really good at what they do

The flight has diverted to AKL for fuel many times, usually planned before departure from DFW. Happens more so in the Northern Summer when winds across the Pacific are stronger.
 
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Bruce
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RE: QFA7 & 8 Dispatch Questions

Mon Oct 28, 2013 9:31 pm

Oh, I didn't realize it was an ER model. That makes a difference. The one that flew on the day I was there was VH-OEJ.
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Starlionblue
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RE: QFA7 & 8 Dispatch Questions

Mon Oct 28, 2013 11:51 pm

Quoting Bruce (Thread starter):
Of course there is a maximum limit of how much fuel can fit in the tanks, I wonder how much they carry?

Max fuel capacity limits payload. On your typical airliner, if you fill the tanks and maximize payload, you'll exceed MTOW.

Quoting Bruce (Reply 2):
o then the maximum published range for an aircraft is not really a "hard" limit?

As longhauler says, very much a grey area.

- The range is in air miles, not ground miles. A couple of hours in a 50-100 knot jetstream in either direction can change ground range by quite a bit.
- It depends on take-off restrictions such as runway length, obstacles in the departure path and temperature.
- You can choose to leave payload on the ground to carry more fuel, or take more payload and less fuel. Pages 55-65 of Boeing's Airplane Performance document give an overview of the trade-offs: http://www.boeing.com/assets/pdf/com...rcial/airports/acaps/7474sec3.pdf. These are generic. In reality, every single aircraft will have specific figures since they're not all the same weight.
- Long haul flights far from diversions may use different rules for alternate fuel, meaning they carry proportionally less fuel relative to the distance than a short haul flight close to alternates.
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sunrisevalley
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RE: QFA7 & 8 Dispatch Questions

Tue Oct 29, 2013 12:19 am

Quoting Bruce (Thread starter):
Quoting Bruce (Thread starter):
QFA8 DFW-BNE is planned at 8713sm. Yesterday's run flew 8561sm, the day before flew 8357sm.
QFA7 SYD-DFW is enroute now, planned at 8585sm. In fact, the last 5 days of QFA7 have all been 8500-8800sm.

The flight time is a more accurate marker in my view. This tells you what the ESAD ( Equivalent still air distance) was for the day. The range of 7670nm at max passenger payload with no winds calls for a flight time of ~15hr 36m. So for any flight time greater than this passenger payload was left behind if the aircraft was full. Conversely less time than this, payload above max passenger load could be added. From Boeings ACAP sheets the standard 3-class 744ER shows 416-seats so I assume the max distance of 7670nm is based in this seat count. But I believe QF have this type set up for 364-seats so I expect their range is something more than 7670nm.
Checking the last 90 days on Flightaware the longest elapsed time was 16hr 20min The predominant range is from 15hr 42m to 16hrs.

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